1. Field of the Invention
The present invention relates to a digital camera displaying an image that is being shot, and more particularly, to a digital camera in which the optical path is split so that light from the taking lens is directed to an optical finder.
2. Description of the Related Art
Generally, digital cameras are provided with a display such as a liquid crystal display, and the display is used for displaying shot and recorded images for the purpose of reproduction and for displaying the image that is being shot. The user can set the composition and confirm the focus condition while viewing the displayed image that is being shot, that is, a live view. Thus, the display functions as a video finder.
Some digital cameras are provided with an optical finder in addition to the display. Digital cameras provided with an optical finder include a separate type in which light is directed to the finder without passing through the taking lens, and a single-lens reflex (SLR) type in which light having passed through the taking lens is reflected to be directed to the finder. In the separate type, a parallax is caused between the finder and the taking lens, whereas in the SLR type, inherently, no parallax is caused.
The SLR type is provided with a prism disposed on the optical path leading from the taking lens to an image sensing device which prism reflects part of the light having passed through the taking lens and transmits the remainder of the light, and a pentagonal prism directing the reflected light to the user's eye and erecting the viewed image. In this structure, the optical finder and the video finder can be used at the same time. However, the light directed to the image sensing device is always part of the light having passed through the taking lens, so that excellent images cannot be provided in shooting under low light conditions.
As well known, in SLR cameras in which silver halide film is exposed, it has conventionally been performed to obliquely dispose a totally reflecting mirror on the optical path leading from the taking lens to the film and pivot the mirror so as to retract from the optical path. The mirror is situated on the optical path until immediately before shooting, that is, film exposure so that light is reflected toward the pentagonal prism. The mirror is retracted from the optical path at the time of shooting so that light is directed to the film, and is advanced onto the optical path immediately after shooting. Mirrors of this type are called quick return mirrors.
Digital cameras provided with such a quick return mirror have also been commercialized. In these cameras, the use of an optical finder and shooting of bright images are both achieved. However, in this structure, the display cannot be used as the finder while the totally reflecting mirror is situated on the optical path in order to use the optical finder, because no light is incident on the image sensing device during this period.
To solve this problem, a digital camera having a half mirror as the quick return mirror has been proposed. Light is incident on the image sensing device both when the half mirror is situated on the optical path and when it is retracted from the optical path, so that shooting and display can be always performed. The optical finder can be also used while the half mirror is situated on the optical path. When an image to be recorded is shot, all the light from the taking lens can be used for shooting by retracting the half mirror from the optical path.
However, in the digital camera having a half mirror as the quick return mirror, differences in brightness among parts are caused in images shot while the mirror is moving to retract from the optical path and while the mirror is moving to advance onto the optical path. This is because while the mirror is moving, the mirror covers only part of the optical path and because of this, light from the taking lens is directly incident on part of the image sensing device and light whose quantity has been reduced by passing through the half mirror is incident on the remainder of the image sensing device. When such images are displayed on the display, differences in brightness are clearly recognized, so that an impression that noises are caused in a series of live views on the display is given to the user.
On the other hand, there is a control method in which a live view is displayed and the half mirror used as the quick return mirror is held on the optical path even when an image to be recorded is shot. In this case, although only part of the light having passed through the taking lens is used for shooting like in the structure in which the optical path is split by the prism, the problem that differences in brightness among parts are caused in images shot while the mirror is moving is solved. However, in that case, since no specific change is caused in the displayed images, the user who provided an image recording instruction by operating the shutter release button cannot be sure that the operation was correctly performed.
By displaying the images in which there are differences in brightness among parts, the user can be informed that the image to be recorded has been shot. However, the defect that the impression of noises being caused is given weight more than the advantage, so that it can be said that is it undesirable to display the images shot while the mirror is moving.
Generally, when an image other than an image to be recorded is shot, the diaphragm is fully opened to provide a bright finder image, and only when an image to be recorded is shot, the aperture of the diaphragm is adjusted to perform exposure control. Including such control, when an image to be recorded is shot, the number of preparations to be made is larger than when an image other than an image to be recorded is shot. However, when the live view display is continued even after the user provides a recording instruction, it is necessary to perform processing to provide the live view display in addition to the preparations for shooting of the image to be recorded, so that the start of shooting of the image to be recorded is apt to be delayed.
The present invention is made in view of these problems, and an object thereof is to provide a digital camera using an optical finder and a video finder at the same time, said digital camera being capable of always displaying stable images.
Another object of the present invention is to provide a digital camera capable of informing the user that an image to be recorded has been shot, without discomforting the user.
Yet another object of the present invention is to provide a digital camera capable of promptly responding to the user's instruction to record an image.